Don't shoot the messenger. Dashboard is just displaying the alert that Prometheus/AlertManager is reporting. The alert definition is here <https://github.com/ceph/ceph/blob/3993779cde9d10512f4a26f87487d11103ac1bd0/monitoring/ceph-mixin/prometheus_alerts.yml#L342-L351>. As you may see, it's based on the status of the Prometheus "ceph" scrape job. This alert is vital, because if the "ceph" job is not scraping metrics from the "mgr/prometheus" module, no other Ceph alert condition will be detected, therefore creating a false sense of confidence. You may start having a look at Prometheus and/or Alertmanager web UIs, or checking their logs. Kind Regards, Ernesto On Tue, Apr 15, 2025 at 7:28 PM Tim Holloway <timh@mousetech.com> wrote:
Although I've had this problem since at least Pacific, I'm still seeing it on Reef.
After much pain and suffering (covered elsewhere), I got my Prometheus services deployed as intended, Ceph health OK, green across the board.
However, over the weekend, the dreaded "CephMgrPrometheusModuleInactive" alert has returned to the Dashboard. "The mgr/prometheus module at dell02.mousetech.com:9283 is unreachable."
It's a blatant lie.
I still get "Ceph HEALTH_OK". All monitor status command show everything running. Checking ports on the host says it's listening.
More to the point, I can send my desktop browser to http://dell02.mousetech.com:9283 and get a page that will allow me to see the metrics. So everyone can see it but the Dashboard!
I did have some issues when the other prometheus host couldn't resolve the hostname, but I fixed that for all ceph hosts and it was green for days. Now the error is back. Restarting Prometheus didn't help.
How is the Dashboard hallucinating this???
Tim _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io